[Elecraft] KPA500 and K3 SWR meters disagree

[Jack Brindle]

Jeff;

Do I understand that for the first test you are driving the antenna through the KPA500 and KAT500 (with KAT500 in bypass)? If so, it makes a lot of sense that you will see different SWR. The KPA and KAT are providing a completely different load for the K3. The better test is to feed the antenna directly from the K3 without the KPA and KAT in-line. I would expect you to see a closer match at that point, although I doubt they will ever be identical due to the differences in the directional couplers in the K3 vs the KAT500 (and KPA500 for that matter).

Jack, W6FB


> On Jun 2, 2018, at 8:48 AM, jeff griffin <kb2m at arrl.net> wrote:
> 
> I recently brought my KPA/KAT500 north for the summer and hooked up to my trapped multiband fan dipole that I use here in NJ. I leave my K3 here for remote use and use the amp at my winter home in Florida to use with my Flex 6500 with a Steppir Vertical antenna without the KAT500 tuner. When I got up here I installed the KIO3B option. The install went well with no issues, all looked good so I connected the K3, P3, KAT500, and KPA500 with the Elecraft provided cable set like I do every year. 
> 
> The issue I'm having is an SWR difference between the KAT500 and the K3. For example if I use the K3's internal tuner I can on a chosen frequency achieve an SWR of 1/1. I the put the internal K3 tuner in bypass mode and take the KAT500 out of bypass and set to auto. I then use the xmit button on the K3 to create a tune signal to be sent to the KAT500. The K3 then shows a 1/1, the KAT500 about the same but the KPA500 which is in STBY mode shows around 3/1. What this causes to happen is the Amp will fault out if I try to use any power output. If I check the antenna with a trusted SWR meter I see 1.3/1 at the frequency of use. I upgraded the firmware in all the devices in use, I also did a reset of the KAT's stored frequencies memory, and checked both the amp and tuner with the utility programs. I'm going to call Elecraft on Monday, anyone have any ideas in the meantime I can try?
> 
> 73 Jeff kb2m   
> 
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